In recent years, optical computing techniques have been developed for applications in the oil and gas Industry in the form of optical sensors on downhole or surface equipment to evaluate a variety of fluid properties. In general, an optical computing device is a device configured to receive an input of electromagnetic radiation from a sample and produce an output of electromagnetic radiation from a processing element, also referred to as an optical element, wherein the output reflects the measured intensity of the electromagnetic radiation. The optical element may be, for example, a narrow band optical element or an Integrated Computational Element (“ICE”) (also known as a Multivariate Optical Element (“MOE”).
Fundamentally, optical computing devices utilize optical elements to perform calculations, as opposed to the hardwired circuits of conventional electronic processors. When light from a light source interacts with a substance, unique physical and chemical information about the substance is encoded in the electromagnetic radiation that is reflected from, transmitted through, or radiated from the sample. Thus, the optical computing device, through use of the ICE core and one or more detectors, is capable of extracting the information of one or multiple characteristics/properties or analytes within a substance and converting that information into a detectable output signal reflecting the overall properties of a sample. Such characteristics may include, for example, the presence of certain elements, compositions, fluid phases, etc. existing within the substance.
Therefore, traditional optical computing devices analyze the measured intensity of sample-interacted radiation in order to determine a sample characteristic of interest. In other words, traditional computing devices are intensity-dependent. As a result, traditional computing devices in some instances can be limited in a number of ways. First, for example, such devices may have a spectral range covering a low absorbing region of the analyte. Second, only one observable, wavelength-dependent variable per analyte is measured. Third, in some cases, elaborate calibration schemes may be needed to correct for radiometric effects. Fourth, such devices can have sensitivity issues resulting from low or fluctuating light intensities and scattering.
Accordingly, there is a need in the art for an intensity-independent optical computing device useful to detect and monitor sample characteristic data in a desired environment.